Virtual Reality (VR) content is intended to provide an immersive experience in which a user is apparently surrounded by and interacts with a virtual environment constructed from actual or computer-generated images. The original source images from which VR content is constructed correspond to different views from the user's apparent location at the center of the environment (e.g., front, back, left, right, etc.). In the typical work flow by which VR content is generated, these images are combined in a process known as “stitching” to form a two-dimensional (2D) representation (using, for example, polygonal or equirectangular projection) in which each of the images corresponds to a portion of a three-dimensional (3D) shape such as, for example, a cube or a cylinder. The 2D representation is then compressed using any of a variety of encoding techniques such as, for example, H.265/High Efficiency Video Coding (HEVC) or H.264/MPEG-4 Advanced Video Coding (H.264).
When VR content is decoded for playback, the 2D representation is scaled to a playback projection space (e.g., a spherical space) resulting in compression of the image data for pixels associated with various parts of the polygonal or cylindrical projection space to fit the playback projection space. Particularly for parts of the images that are near a vertex of the polygonal projection space or the poles of a cylindrical projection space, this can result in visual artifacts such as moiré patterns and false detail that detract from the user's experience.